The present invention relates to an ultrasonic diagnostic apparatus for scanning the three-dimensional region of an object to be examined with ultrasonic pulses to perform various diagnoses using the resultant information.
Various apparatuses are available as medical applications of ultrasonic waves. The most frequently used is an ultrasonic diagnostic apparatus which obtains tomographic images of soft tissues of living bodies by using the ultrasonic pulse reflection method. This ultrasonic diagnostic apparatus displays a tomographic image of a tissue by a noninvasive examination method. Compared with other diagnostic apparatuses such as an X-ray diagnostic apparatus, an X-ray computer tomographic apparatus (X-ray CT), a magnetic resonance imaging apparatus (MRI), and a nuclear medicine diagnostic apparatus (e.g., a gamma camera and SPECT), an ultrasonic diagnostic apparatus has the advantages that it can display images in real time, is small and inexpensive, has high safety with no exposure to x-rays, and is capable of blood flow imaging by using the ultrasonic Doppler method.
For these reasons, ultrasonic diagnoses are extensively performed in examinations of hearts, abdomens, mammary glands, and urinary organs, and in obstetrics and gynecology. In particular, heart beats and the motions of an unborn child can be displayed in real time with a simple operation of bringing an ultrasonic probe into contact with the body surface, and the safety is high. Therefore, examinations can be repetitively performed and can also be readily performed even on the bedside.
It is also possible to display the velocity distribution of a blood flow which moves closer to or away from a vibrator by using the ultrasonic Doppler method and display the power value distribution of a blood flow echo signal by using the power Doppler method. In particular, the power Doppler method can detect the perfusion of a blood vessel system with high sensitivity and hence is used to diagnose peripheral blood flow abnormality of a kidney and hepatoma.
In the field of these ultrasonic diagnoses, as in X-ray CT and MRI, needs for three-dimensional images are increasing. Three-dimensional images have information in the direction of depth in addition to planar information obtained from two-dimensional tomographic images. Accordingly, three-dimensional images are expected to allow an operator to more clearly observe the shape of a tissue, circulation of the blood, and the like.
Three-dimensional information is acquired as follows. That is, a position sensor attached to a probe is used to obtain position information and corresponding image information at the same time. After that, a three-dimensional image is reconstructed on the basis of the position information. Many methods have been proposed so far, and it has become possible to reconstruct and display three-dimensional images within very short time periods with the aid of increased operating speeds of recent CPUs.
Although the operating speeds of CPUs have increased, however, it is currently still impossible to reconstruct and display a three-dimensional image in real time, or in almost real time, from three-dimensional echo data input by three-dimensional scan. In practice, therefore, it is necessary to employ a method which reconstructs and displays a three-dimensional image after three-dimensional data is input and scan is stopped. Accordingly, in ordinary diagnoses, conventional two-dimensional tomographic images are observed in real time in most cases.